This invention relates generally to a foundation system for a premanufactured building that is supported above the ground on a plurality of piers, with the piers supporting two or more horizontally extending parallel joists of the building. More particularly, the invention relates to a stabilization system for the foundation for such a building.
Premanufactured building structures such as mobile homes, trailers, prefabricated houses and the like are manufactured at a central manufacturing site, and upon completion the structures are moved to a location where they are to be permanently located and occupied. Because the typical manufactured structure is designed to be easily moved from the site where it is manufactured to its permanent location, the structure is not originally built upon a permanent foundation at the manufacturing site. Rather, the structure typically is constructed upon a pair of parallel, horizontally extending I-beam joists. The joists are displaced inwardly from the opposing side walls of the manufactured structure, and temporary wheels are attached to the joists so that the manufactured structure can be transported over public highways to its installation site, where the structure likely will be mounted on piers, such as concrete blocks, pilings, or stabilizing jacks. It is important that the structure be anchored in position on the piers, typically with the use of ground anchors and ties extending from the ground anchors to the joists or other framework of the structure, so as to avoid the structure being shifted off of its piers by strong winds or seismic action. Serious damage to the manufactured structure and even human injury can occur if a structure is inadvertently shifted off of its piers or tilted over.
Various types of stabilizing devices have been used to stabilize such manufactured structures, to keep the structures from moving in response to wind forces and earth movement. The vertical support for the manufactured structure usually is provided by the piers located under the parallel joists of the main frame of the structure, with the piers being spaced longitudinally along the parallel joists at approximately 8 feet intervals. The piers typically are placed upon flat planar foundation platforms each having a much larger surface area than the pier itself and which stabilizes the pier at its interaction with the ground surface.
Lateral and upward movement off of the piers is resisted by tie down straps that tie the support joists of the structure to ground fixtures or to ground anchors that are either permanently or temporarily inserted into the ground. A traditional approach to providing wind storm protection for manufactured structures includes a ground anchor having a shank with one or more helical plates at the bottom of the shank that can be rotated to move the anchor into the ground, and cold rolled steel strapping installed as a diagonal tie between the anchor head and the lower main frame of the manufactured structure. Anchors of this type are taught in U.S. Pat. Nos. 5,758,460; 5,697,191; 5,784,844; and 5,850,718.
While the foregoing stabilizing systems have been successful in reliably tying down manufactured structures, the prior art systems continue to need improvement to provide inexpensive and easy to install and safe stabilization systems to avoid the buildings from shifting laterally and/or longitudinally off of their piers. It is believed that if movement of the building structure with respect to the piers can be avoided, most of the problems of supporting the building structure can be avoided.
It is to the above noted problem that this invention is directed.
Briefly described, the present invention provides a stabilization system for the foundation of a premanufactured building structure that braces the joists of the building structure with respect to foundation platforms placed beneath the building structure. Each foundation platform typically supports a pier, with the lower end portion of the pier being mounted on a foundation platform and the upper portion of the pier being placed in supporting relationship with respect to a supporting joist of the building structure. In this manner, the weight of the building structure is applied downwardly through the pier to the foundation platform and distributed through the foundation platform to the ground beneath the platform. Thus, the weight of the building structure stabilizes the foundation platform.
One or more diagonally extending struts are connected between the foundation platform and a joist of the building, with each strut connected at its lower end to the foundation platform and sloped upwardly from the foundation platform and adapted for connection at its upper end to a joist of the building structure. The weight of the building structure and the shape of the foundation platform keep the foundation platform from moving in response to the diagonal forces applied to the foundation platform by the strut.
Each diagonal strut is arranged with respect to the foundation platform so as to apply the forces of compression received from the joists of the building structure in a direction sloped downwardly to the foundation platform. These forces are stabilized with the weight of the building as applied to the foundation platform, so as to spread the sum of the forces across the foundation platform. The weight of the building applied to the foundation platform and the configuration of the foundation platform are sufficient to avoid lateral movement, tilting and turning of the foundation platform in response to the diagonal forces applied by the diagonal struts.
In a preferred embodiment, the foundation platform includes a body portion that is to be applied against the ground beneath the building structure. Panels extending from opposed edges of the body portion and angled with respect to the body portion form cleats that extend into the ground at the edges of the body portion. While the cleats may take several configurations, a preferred embodiment of the cleats is that the cleats are formed as walls so as to have large cross-sectional areas that have the potential of laterally engaging the ground beneath the body portion of the foundation platform.
When the foundation platforms are placed on the ground, at least one of the cleat walls of the foundation platform is oriented transversely with respect to the length of the strut. When the strut applies its diagonal force against the foundation platform, the transverse cleat walls resist horizontal movement of the foundation platform and the ground resists vertical movement, thereby resisting the force of the strut. This, in turn, resists the movement of the joist to which the upper end of the strut is connected, thereby stabilizing the foundation system and, in turn, the building structure. This is accomplished without applying horizontal forces against the pier.
Because it is desirable to construct the pier of inexpensive materials, such as concrete blocks, a typical pier is strong in a vertical dimension in that it can hold large weights, but is relatively weak in horizontal force resistant properties. Therefore, the invention disclosed herein avoids applying horizontal forces to the pier, enabling the builder to utilize less expensive materials in the pier.
In one embodiment of the invention, the lower end portion of the strut is mounted to the foundation platform at a position equidistant between the opposed transverse cleat walls. With this arrangement the forces applied through the strut to the foundation platform are more equally applied to the opposed transverse cleat walls, avoiding tilting and turning of the foundation platform.
Other embodiments of the invention employ two struts having their lower ends placed in straddling relationship with respect to the pier mounted on the foundation platform, on opposite sides of the position where the weight of the building is applied to the foundation platform. Again, this tends to balance the load applied to the foundation platform, with the weight of the building being applied to the central portion of the platform, thereby avoiding the tilting, turning and/or deterioration of the foundation platform in response to the diagonal forces of compression being applied thereto by the diagonal struts.
Other embodiments of the invention include struts mounted at their respective lower ends to the foundation platform in relationships where the forces applied through the struts to the foundation platform are equally distributed in the foundation platform. The struts can be sloped upwardly in various directions to the same joist of the building structure that is supported by the pier or to adjacent ones of the joists.
In the preferred embodiment of the invention, the foundation platform is fabricated of a single piece of sheet material, preferably high grade steel. The foundation platform includes a centrally positioned rectangular flat body portion arranged for placement in flat abutment with the ground, and cleat walls extending from the edges of the body portion and turned toward the ground for extending downwardly into the ground. The cleat walls avoid horizontal movement of the foundation platform in response to the forces applied thereto by the struts and the joists of the building structure while the weight of the building applied to the central body portion avoids vertical movement.
Typically, the improved stabilization system described herein is combined with ground anchors and tie down straps and other conventional equipment needed to avoid lifting of the building structure off the piers and lateral movement of the building structure.
Therefore, it is an object of the present invention to provide an improved stabilization system for the foundation of a premanufactured building structure that is easy to install, inexpensive to produce, and which provides improved stabilization to the building structure.
Another object of this invention is to provide an improved stabilization system for premanufactured building structures that provide resistance to horizontal movement of the building structure with respect to the piers that support the building structure, without applying horizontal forces to the piers themselves.
Another object of this invention is to provide an improved foundation system for a premanufactured building structure that utilizes a foundation platform positioned on the ground with piers mounted thereon, and with struts extending diagonally from the building structure downwardly to the support platforms, with the weight of the building and the configuration of the foundation platform resisting horizontal movement of the building structure.
Another object of the invention is to provide an improved foundation for a premanufactured building structure that utilizes the weight of the building structure to retard horizontal movement of the building.
Other objects, features and advantages of this invention will become apparent upon reading the following specification, when taken in conjunction with the accompanying drawings.